OZ, a virtual world connected to the internet, has become extremely popular worldwide as a spot for people to engage in a large variety of activities, such as playing sports or shopping, through avatars created and customized by the user. OZ also possesses a near impenetrable security due to its strong encryption, ensuring that any personal data transmitted through the networks will be kept safe in order to protect those who use it. Because of its convenient applications, the majority of society has become highly dependent on the simulated reality, even going as far as entrusting the system with bringing back the unmanned asteroid explorer, Arawashi.

Kenji Koiso is a 17-year-old math genius and part-time OZ moderator who is invited by his crush Natsuki Shinohara on a summer trip. But unbeknownst to him, this adventure requires him to act as her fiancé. Shortly after arriving at Natsuki's family's estate, which is preparing for her great-grandmother's 90th birthday, he receives a strange, coded message on his cell phone from an unknown sender who challenges him to solve it. Kenji is able to crack the code, but little does he know that his math expertise has just put Earth in great danger.

[Written by MAL Rewrite]

Chise Hatori, a 15-year-old Japanese girl, was sold for five million pounds at an auction to a tall masked gentleman. Abandoned at a young age and ridiculed by her peers for her unconventional behavior, she was ready to give herself to any buyer if it meant having a place to go home to. In chains and on her way to an unknown fate, she hears whispers from robed men along her path, gossiping and complaining that such a buyer got his hands on a rare "Sleigh Beggy."

Ignoring the murmurs, the mysterious man leads the girl to a study, where he reveals himself to be Elias Ainsworth—a magus. After a brief confrontation and a bit of teleportation magic, the two open their eyes to Elias' picturesque cottage in rural England. Greeted by fairies and surrounded by weird and wonderful beings upon her arrival, these events mark the beginning of Chise's story as the apprentice and supposed bride of the ancient magus.

[Written by MAL Rewrite]

Having freed a myriad of women from the runaway spirits possessing their hearts, the "God of Conquest" Keima Katsuragi is confronted with a new task: find the Jupiter Sisters, the goddesses that sealed Old Hell in the past. Diana, the goddess that resides inside his childhood friend Tenri Ayukawa, explains that they have taken shelter in the hearts of the girls he had assisted previously. Moreover, once Diana and her sisters are reunited, their power can seal the runaway spirits away for good and relieve Keima of his exorcising duties. Though he is initially reluctant to get involved in yet another chore, everything changes when tragedy befalls one of the hosts. Discovering that the goddesses are being targeted by a mysterious organization known as Vintage, Keima is caught in a race against time to reunite the sisters and rescue the girl who has already fallen prey. With deeper resolve than ever before, Keima works together with demons Elsie and Haqua to recapture the hearts of the girls he had charmed in the past. However, the road ahead is a difficult one, as he is soon met with the consequences of his previous conquests. [Written by MAL Rewrite]

Kazuya Kujou is a foreign student at Saint Marguerite Academy, a luxurious boarding school in the Southern European country of Sauville. Originally from Japan, his jet-black hair and dark brown eyes cause his peers to shun him and give him the nickname "Black Reaper," based on a popular urban legend about the traveler who brings death in the spring. On a day like any other, Kujou visits the school's extravagant library in search of ghost stories. However, his focus soon changes as he becomes curious about a golden strand of hair on the stairs. The steps lead him to a large garden and a beautiful doll-like girl known as Victorique de Blois, whose complex and imaginative foresight allows her to predict their futures, now intertwined. With more mysteries quickly developing—including the appearance of a ghost ship and an alchemist with the power of transmutation—Victorique and Kujou, bound by fate and their unique skills, have no choice but to rely on each other. [Written by MAL Rewrite]